1. Field of the Invention
The present invention relates to a magnetizing method, a permanent magnet magnetized by the method, and a motor equipped with the permanent magnet. Particularly, the present invention relates to a permanent magnet suitable for a rotor magnet of a spindle motor obtained by multipole magnetization and a magnetizing method thereof.
2. Background Art
A magnetization waveform of a permanent magnet for driving a motor largely affects conversion efficiency of torque, vibration, and energy of the motor, or the like. It is well-known that by making the magnetization waveform into a ideal sine waveform, the property can be improved.
Therefore, improvements in the magnetization waveform, heretofore, have been performed by contriving a shape of a yoke in a magnetizing device. Nevertheless, remaining high-order harmonic components in the magnetization waveform cannot be avoided.
Furthermore, with regard to a permanent magnet, its surface is easy to corrode, so that plating or coating is applied for the purpose of surface protection. For example, a technique of applying corrosion-resisting plating on a surface of a rare earth-B—Fe based permanent magnet or the like has been employed.
These plating and coating are intended solely to improve corrosion resistance. For the plating material, a ferromagnetic material such as Ni has normally been used in order not to impair the function of the permanent magnet.
However, the coating applied to the permanent magnet has not contributed to the improvement in the magnetization waveform.